Return to ufs_machdep.c CVS log

Up to [CSRG BSD Unix] / 43BSDTahoe / sys / tahoe

Initial revision

/*
 * Copyright (c) 1983, 1988 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the University of California, Berkeley.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 *	@(#)ufs_machdep.c	7.2 (Berkeley) 6/29/88
 */

#include "param.h"
#include "systm.h"
#include "dir.h"
#include "user.h"
#include "buf.h"
#include "conf.h"
#include "proc.h"
#include "seg.h"
#include "vm.h"

#include "pte.h"

/*
 * Machine dependent handling of the buffer cache.
 */

/*
 * Expand or contract the actual memory allocated to a buffer.
 * If no memory is available, release buffer and take error exit
 */
allocbuf(tp, size)
	register struct buf *tp;
	int size;
{
	register struct buf *bp, *ep;
	int sizealloc, take;

	sizealloc = roundup(size, CLBYTES);
	/*
	 * Buffer size does not change
	 */
	if (sizealloc == tp->b_bufsize)
		goto out;
	/*
	 * Buffer size is shrinking.
	 * Place excess space in a buffer header taken from the
	 * BQ_EMPTY buffer list and placed on the "most free" list.
	 * If no extra buffer headers are available, leave the
	 * extra space in the present buffer.
	 */
	if (sizealloc < tp->b_bufsize) {
		ep = bfreelist[BQ_EMPTY].av_forw;
		if (ep == &bfreelist[BQ_EMPTY])
			goto out;
		notavail(ep);
		pagemove(tp->b_un.b_addr + sizealloc, ep->b_un.b_addr,
		    (int)tp->b_bufsize - sizealloc);
		ep->b_bufsize = tp->b_bufsize - sizealloc;
		tp->b_bufsize = sizealloc;
		ep->b_flags |= B_INVAL;
		ep->b_bcount = 0;
		brelse(ep);
		goto out;
	}
	/*
	 * More buffer space is needed. Get it out of buffers on
	 * the "most free" list, placing the empty headers on the
	 * BQ_EMPTY buffer header list.
	 */
	while (tp->b_bufsize < sizealloc) {
		take = sizealloc - tp->b_bufsize;
		bp = getnewbuf();
		if (take >= bp->b_bufsize)
			take = bp->b_bufsize;
		pagemove(&bp->b_un.b_addr[bp->b_bufsize - take],
		    &tp->b_un.b_addr[tp->b_bufsize], take);
		tp->b_bufsize += take;
		bp->b_bufsize = bp->b_bufsize - take;
		if (bp->b_bcount > bp->b_bufsize)
			bp->b_bcount = bp->b_bufsize;
		if (bp->b_bufsize <= 0) {
			bremhash(bp);
			binshash(bp, &bfreelist[BQ_EMPTY]);
			bp->b_dev = (dev_t)NODEV;
			bp->b_error = 0;
			bp->b_flags |= B_INVAL;
		}
		brelse(bp);
	}
out:
	tp->b_bcount = size;
	return (1);
}

/*
 * Release space associated with a buffer.
 */
bfree(bp)
	struct buf *bp;
{

	bp->b_bcount = 0;
}

This archive runs on limited infrastructure. Preserving old code on modern bandwidth. Automated agents are requested to crawl responsibly.